I. Field of the Invention
This invention relates generally to extendable frame vehicles, and more particularly to extendable frame work vehicles, capable of enhanced performance of a variety of construction, landscaping, residential, agricultural and industrial tasks.
II. Related Art
In recent decades, construction equipment capabilities have increased dramatically as have the variety of specialized machines and vehicles that are useful to persons performing jobs at various worksites. To complete many projects, a variety of such specialized vehicles must be delivered to a specific worksite on large trucks or trailers. These vehicles may include skid steer loaders, front end loaders, backhoes, rough terrain forklifts or any of a large number of trucks and similar devices. Acquiring and transporting such a variety of equipment can be difficult and costly. Further, mastering operation of the many steering and control systems for these different vehicles is known to be an arduous task. It has been frequently recognized, for example, that reducing the number of machines necessary for a particular job would be advantageous. This is especially true when such reduction can be done without sacrificing capabilities of the various machines. A vehicle then, which combines selected useful features of several former vehicles and makes these features even more useful and versatile, would be highly desired and valued by persons in this industry.
Highly maneuverable work vehicles with short wheelbases, such as skid steer vehicles, have proven to be extremely useful for a wide range of agriculture, construction and industrial projects and are considered to be among the most versatile work vehicles available. Such vehicles typically include a rigid frame, independently driven sets of right and left wheels, an operator cab, an engine, a hydraulic system and lift arms to which a variety of attachments can be joined (e.g. buckets, trenchers, etc.). The overwhelming success of these skid steer vehicles can be traced to a large extent to the maneuverability of steering and control, speed, suitability to a variety of environments, interchangeability of attachments and generally rugged design.
Despite the many advantages offered by these vehicles, they also have limitations because of configuration or design. There are also problematic safety considerations. For example, when a skid steer vehicle lifts an item with a boom, bucket or other attachment, the size of the load that can be safely moved may be compromised by the relatively short wheelbase of the conventional skid steer vehicle. The short wheelbase often does not provide a sufficiently stable structure or counterweight to prevent tipping or other unwanted movement. Similarly, traversing steep terrain in a vehicle with such a short wheelbase, particularly when carrying a load, can present problems. Although various trucks and vehicles with wider wheelbases have been used for various tasks in the past, these vehicles generally have greatly diminished maneuverability and agility of operation. Trucks and construction vehicles have been proposed with extendable wheelbases or body members. However, these vehicles generally have a longer steering radius than a skid steer and are less maneuverable. This limits the usefulness of such machines.
Traditional skid steer steering systems also have drawbacks related to the wear and tear they can cause on a work site. Standard operation may cause the vehicle wheels to dig into the ground, particularly if the ground is soft turf. A steering system and design that takes into account and adjusts to a diversity of operating environments and which is compatible with the surface on which it is operated is desired.
Because of the many potential circumstances in which work vehicles must perform, and because of the hazards inherently present in certain construction environments, a vehicle which overcomes such hazards is highly desired. For example, operators of work vehicles of the class are known to attempt to traverse inclines which may be too steep, lift loads that may be too heavy for the circumstances, drive vehicles with unfamiliar controls that are hard to manage or operate in areas where visibility is limited or impaired and may contribute to a situation that is unsafe. The capability to sense and avoid marginal or unsafe situations is clearly important to work vehicle operators. Generally, current designs are not able to cope with these hazards and most present work vehicles provide little ability to adapt or adjust the vehicle to address such dangers. For example, if a front end loader were to become unstable because a load lifted was too heavy, an operator would have little choice but to rely on his or her quick reflexes to rapidly release the load to prevent the vehicle from tipping.
Therefore, it remains desirable to offer a work vehicle which provides greater versatility, effectiveness and safety. An improved work vehicle is needed which overcomes the problems and limitations experienced in past methods and devices.